U.S. patent application number 15/217343 was filed with the patent office on 2017-09-21 for additive manufacturing apparatus and additive manufacturing method.
This patent application is currently assigned to FUJI XEROX CO., LTD.. The applicant listed for this patent is FUJI XEROX CO., LTD.. Invention is credited to Atsuyuki KITAMURA, Atsushi OGIHARA.
Application Number | 20170266863 15/217343 |
Document ID | / |
Family ID | 59855224 |
Filed Date | 2017-09-21 |
United States Patent
Application |
20170266863 |
Kind Code |
A1 |
OGIHARA; Atsushi ; et
al. |
September 21, 2017 |
ADDITIVE MANUFACTURING APPARATUS AND ADDITIVE MANUFACTURING
METHOD
Abstract
An additive manufacturing apparatus includes a discharging unit
that discharges resin powder into a molding tank; a supplying unit
that supplies a fiber into the molding tank; and a solidifying unit
that solidifies at least part of a resin layer including the fiber
and formed in the molding tank.
Inventors: |
OGIHARA; Atsushi; (Kanagawa,
JP) ; KITAMURA; Atsuyuki; (Kanagawa, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
FUJI XEROX CO., LTD. |
Tokyo |
|
JP |
|
|
Assignee: |
FUJI XEROX CO., LTD.
Tokyo
JP
|
Family ID: |
59855224 |
Appl. No.: |
15/217343 |
Filed: |
July 22, 2016 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B29C 48/156 20190201;
B33Y 70/00 20141201; B29C 48/2886 20190201; B29C 64/153 20170801;
B29C 48/18 20190201; B29C 70/14 20130101; B33Y 10/00 20141201; B29L
2031/00 20130101; B29C 64/321 20170801; B29K 2101/12 20130101; B29C
48/16 20190201 |
International
Class: |
B29C 47/06 20060101
B29C047/06 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 17, 2016 |
JP |
2016-054368 |
Claims
1. An additive manufacturing apparatus comprising: a discharging
unit that discharges resin powder into a molding tank; a supplying
unit that supplies a fiber into the molding tank; and a solidifying
unit that solidifies at least part of a resin layer including the
fiber and formed in the molding tank.
2. The additive manufacturing apparatus according to claim 1,
further comprising a heating unit that heats the fiber.
3. The additive manufacturing apparatus according to claim 1,
wherein the fiber supplied by the supplying unit is coated with a
coating material made of resin.
4. The additive manufacturing apparatus according to claim 1,
wherein the supplying unit is able to change a supply
direction.
5. The additive manufacturing apparatus according to claim 1,
wherein the supplying unit supplies the fiber only to a region
which is solidified by the solidifying unit.
6. The additive manufacturing apparatus according to claim 1,
wherein the supplying unit supplies the fiber before the resin
powder is discharged from the discharging unit.
7. The additive manufacturing apparatus according to claim 1,
wherein the supplying unit supplies the fiber after the resin
powder is discharged from the discharging unit.
8. The additive manufacturing apparatus according to claim 1,
wherein the supplying unit supplies the fiber after the
solidification of the resin layer by the solidifying unit is
started and before the solidification of the resin layer is
completed.
9. The additive manufacturing apparatus according to claim 1,
wherein the supplying unit supplies the fiber so that the fiber
extends over a layer interface of the resin layer formed in the
molding tank.
10. The additive manufacturing apparatus according to claim 1,
wherein the resin powder is powder of thermoplastic resin.
11. An additive manufacturing method comprising: discharging resin
powder into a molding tank; supplying a fiber into the molding
tank; and solidifying at least part of a resin layer including the
fiber and formed in the molding tank.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is based on and claims priority under 35
USC 119 from Japanese Patent Application No. 2016-054368 filed Mar.
17, 2016.
BACKGROUND
[0002] The present invention relates to an additive manufacturing
apparatus and an additive manufacturing method.
SUMMARY
[0003] According to an aspect of the invention, there is provided
an additive manufacturing apparatus including a discharging unit
that discharges resin powder into a molding tank; a supplying unit
that supplies a fiber into the molding tank; and a solidifying unit
that solidifies at least part of a resin layer including the fiber
and formed in the molding tank.
BRIEF DESCRIPTION OF THE DRAWINGS
[0004] Exemplary embodiments of the present invention will be
described in detail based on the following figures, wherein:
[0005] FIG. 1 is a schematic side view of an additive manufacturing
apparatus according to a first exemplary embodiment;
[0006] FIGS. 2A to 2C are explanatory illustrations each showing a
molding step of a three-dimensional molded part by the additive
manufacturing apparatus according to the first exemplary
embodiment;
[0007] FIGS. 3A to 3C are explanatory illustrations each showing a
molding step of the three-dimensional molded part by the additive
manufacturing apparatus according to the first exemplary
embodiment;
[0008] FIG. 4 is a schematic side view of an additive manufacturing
apparatus according to a second exemplary embodiment;
[0009] FIGS. 5A to 5C are explanatory illustrations each showing a
molding step of a three-dimensional molded part by the additive
manufacturing apparatus according to the second exemplary
embodiment; and
[0010] FIGS. 6A to 6C are explanatory illustrations each showing a
molding step of the three-dimensional molded part by the additive
manufacturing apparatus according to the second exemplary
embodiment.
DETAILED DESCRIPTION
[0011] Exemplary embodiments of the present invention are described
below in detail with reference to the drawings. For convenience of
description, it is assumed that arrow UP properly shown in each
drawing indicates the upward direction of an additive manufacturing
apparatus 10 and arrow RH properly shown in each drawing indicates
the rightward direction of the additive manufacturing apparatus 10.
Also, it is assumed that the near-side direction toward the paper
face of each drawing indicates the forward direction of the
additive manufacturing apparatus 10.
First Exemplary Embodiment
[0012] First, an additive manufacturing apparatus 10 according to a
first exemplary embodiment is described. As shown in FIG. 1, the
additive manufacturing apparatus 10 includes a molding tank 12 for
molding a three-dimensional molded part M. The molding tank 12
includes an apparatus body 14 having an opening 14A with, for
example, a circular shape; and a disk-shaped molding table 16
provided in the opening 14A of the apparatus body 14. The molding
table 16 is provided movably upward and downward by a known up/down
moving device 18, such as an air cylinder. The molding table 16 has
an outer diameter determined to be able to slide relative to the
inner peripheral surface of the opening 14A.
[0013] A reflector 21 is arranged above the molding tank 12. The
reflector 21 may change its angle by a mechanism (not shown). A
laser device 20 is arranged at a proper position. The laser device
20 serves as a solidifying unit that emits a laser beam Lc that
provides scanning while reflected by the reflector 21. An example
of the laser beam Lc emitted from the laser device 20 may be a
laser beam of a carbon dioxide laser with a wavelength (for
example, about 10 .mu.m) that is likely absorbed by powder P made
of resin (hereinafter, referred to as "resin powder").
[0014] Further, a screen member 22 is arranged above the molding
tank 12. The screen member 22 serves as an example of a discharging
unit that discharges the resin powder P into the molding tank 12. A
mesh plate 23 in a fine mesh form and an open/close plate (not
shown) that opens and closes the mesh plate 23 are arranged at a
bottom portion of the screen member 22. The open/close plate is
opened at a position above the molding tank 12, and the resin
powder P passing through the mesh plate 23 is discharged into the
molding tank 12. An example of the resin powder P may be powder of
thermoplastic resin.
[0015] Also, the screen member 22 is movable in a radial direction
(the left-right direction in the drawing) of the molding tank 12,
by a known moving mechanism (not shown). That is, the screen member
22 may take positions including a discharge position at which the
screen member 22 is located above the molding tank 12 and
discharges the resin powder P into the molding tank 12 (the mesh
plate 23 is opened by the open/close plate), and a retraction
position at which the screen member 22 is retracted from the
position above the molding tank 12 and does not discharge the resin
powder P into the molding tank 12 (the mesh plate 23 is closed by
the open/close plate).
[0016] Also, a nozzle member 24 is arranged above the molding tank
12. The nozzle member 24 serves as an example of a supplying unit
that ejects and supplies plural fibers F (see FIGS. 2A to 3C) into
the molding tank 12 at once. An example of the fibers F may be
carbon fibers or glass fibers. Regarding the fibers F in this
exemplary embodiment, for example, in case of carbon fibers, the
fibers F to be used have a diameter in a range from 0.005 mm to
0.01 mm, a length in a range from 0.5 mm to 1.0 mm, and a larger
thickness than the layer thickness of a single layer of the resin
powder P (described later).
[0017] The nozzle member 24 is mounted at a distal end portion of a
robot arm 26, rotatably around a direction intersecting with the
up-down direction as the axial direction. The robot arm 26 is
movable in the radial direction (the left-right direction) of the
molding tank 12. This movement may handle a change in the supply
position and supply direction of the fibers F to be supplied into
the molding tank 12 in accordance with molding data of the
three-dimensional molded part M to be molded.
[0018] That is, since the robot arm 26 moves in the radial
direction of the molding tank 12, the nozzle member 24 is able to
supply the fibers F only to an area where the three-dimensional
molded part M is formed (a region to be solidified by the laser
device 20). Since the nozzle member 24 rotates around the direction
intersecting with the up-down direction as the axial direction,
this rotation may handle a change in the angle (the supply
direction) of the fibers F to be supplied to the area where the
three-dimensional molded part M is formed.
[0019] Also, the fibers F to be supplied by the nozzle member 24
are coated with a coating material made of resin (hereinafter,
referred to as resin coating material, not shown). Hence, the
nozzle member 24 includes a heater 28 serving as an example of a
heating unit that heats and melts the fibers F together with the
coating material. That is, in this first exemplary embodiment, the
fibers F coated with the resin coating material are supplied into
the molding tank 12 by fused deposition molding.
[0020] An operation with the additive manufacturing apparatus 10
according to the first exemplary embodiment configured as described
above is described below.
[0021] The molding table 16 is arranged at an upper portion side of
the molding tank 12 by the up/down moving device 18. In this state,
when the screen member 22 is arranged at the discharge position
located above the molding tank 12 and when the open/close plate is
opened, the resin powder P is discharged into the molding tank 12.
Accordingly, as shown in FIG. 2A, a layer of the resin powder P,
that is, a lowermost resin layer Ps0 is formed on the molding table
16 in the molding tank 12 (the lowermost resin layer Ps0 is
indicated by oblique lines). Then, after the resin layer Ps0 is
formed on the molding table 16, the open/close plate is closed, the
screen member 22 is retracted to the retraction position, and the
nozzle member 24 supplies plural fibers F to the resin layer
Ps0.
[0022] As described above, in the additive manufacturing apparatus
10 according to the first exemplary embodiment, the configuration
is divided into the screen member 22 that discharges the resin
powder P and the nozzle member 24 that supplies the fibers F.
Hence, as compared with a configuration not divided into the screen
member 22 that discharges the resin powder P and the nozzle member
24 that supplies the fibers F, the orientation and mixture ratio of
the fibers F in the three-dimensional molded part M (condensation
of the fibers F with respect to the resin powder P) are properly
set.
[0023] In particular, since the nozzle member 24 is able to change
the supply position and supply direction in accordance with the
molding data of the three-dimensional molded part M, as compared
with a configuration that is not able to change the supply position
or supply direction, the orientation and mixture ratio of the
fibers F in the three-dimensional molded part M are properly
controlled. Also, the fibers F to be supplied by the nozzle member
24 are coated with the resin coating material. Hence, as compared
with a configuration in which the fibers F are not coated with the
resin coating material, the fibers F are smoothly supplied into the
molding tank 12.
[0024] Further, the nozzle member 24 includes the heater 28 that
heats the fibers F together with the coating material. For example,
the fibers F supplied to the resin layer Ps0 are cooled,
solidified, and hence fixed after the supply. Hence, as compared
with a configuration not including the heater 28 that heats the
fibers F, the orientation of the fibers F in the three-dimensional
molded part M is properly ensured.
[0025] After the supply with the fibers F by the nozzle member 24
is ended, the screen member 22 is arranged at the discharge
position again, and as shown in FIGS. 2B and 2C, the resin powder P
is discharged into the molding tank 12 and laminated. That is, a
resin layer Ps1 is formed on the resin layer Ps0. After the screen
member 22 is retracted to the retraction position, as shown in FIG.
2C, the area supplied with the fibers F in the resin layer Ps1 is
molten or sintered and solidified (a solidified portion Mh is
formed) by the laser beam Lc (see FIG. 1), which is emitted from
the laser device 20 and provides scanning while reflected by the
reflector 21.
[0026] As described above, if only the area supplied with the
fibers F in the resin layer Ps1 is solidified by the laser beam Lc,
as compared with a configuration in which the nozzle member 24
supplies the fibers F to a region other than the region to be
solidified by the laser beam Lc, the consumption of the fibers F is
decreased, and hence the manufacturing cost of the
three-dimensional molded part M is decreased. Also, when the resin
powder P, which is not solidified and remains in the molding tank
12 after the three-dimensional molded part M is removed, is
collected, the resin powder P not including the fibers F may be
collected, and the resin powder P is smoothly sent to the screen
member 22 (or a coater 32, described later) again.
[0027] Then, as shown in FIG. 3A, the nozzle member 24 supplies
plural fibers F to the solidified portion Mh formed in the molding
tank 12. At this time, since the fibers F are heated and molten by
the heater 28, the fibers F are cooled after the supply, and hence
fixed at the solidified portion Mh. As described above, as long as
the fibers F are supplied before the resin powder P is discharged
except for the lowermost resin layer Ps0, as compared with a
configuration that supplies the fibers F after the resin powder P
is discharged, the orientation of the fibers F is stabilized.
[0028] Alternatively, the nozzle member 24 may supply the fibers F
in a state in which the area supplied with the fibers F in the
resin layer Ps1 is molten by the laser beam Lc (after the
solidification of the resin layer Ps1 by the laser beam Lc is
started and before the solidification of the resin layer Ps1 is
completed). Accordingly, as compared with a configuration in which
the nozzle member 24 supplies the fibers F after the solidification
of the area supplied with the fibers F in the resin layer Ps1 is
completed (as compared with a configuration in which the fibers F
are heated and fixed at the solidified portion Mh), the coupling
force between the fibers F and the resin powder P is increased.
[0029] Then, as shown in FIG. 3B, the screen member 22 is arranged
at the discharge position again, and the resin powder P is
discharged into the molding tank 12 and laminated. That is, a resin
layer Ps2 is formed on the resin layer Ps1. After the screen member
22 is retracted to the retraction position, as shown in FIG. 3C,
the area supplied with the fibers F in the resin layer Ps2 is
molten or sintered and solidified (the solidified portion Mh is
increased) by the laser beam Lc, which is emitted from the laser
device 20 and provides scanning while reflected by the reflector
21.
[0030] By successively repeating the above-described steps, the
three-dimensional molded part M as shown in FIG. 1 is formed in the
molding tank 12. Although the illustration is omitted, as the resin
powder P discharged from the screen member 22 is laminated on the
molding table 16, the molding table 16 is gradually moved downward
by the up/down moving device 18.
[0031] Also, since the fibers F have a large length (for example,
the length is 0.7 mm which is larger than a resin layer Ps), as
compared with a configuration in which the fibers F have a small
length (for example, the length is 0.1 mm which is smaller than the
resin layer Ps), the tensile strength of the three-dimensional
molded part M is increased. Also, since the resin powder P is the
thermoplastic resin powder, as compared with a configuration in
which the resin powder P is not the thermoplastic resin powder, the
coupling force between the fibers F and the resin powder P is
increased.
[0032] Also, as shown in FIG. 3C, the nozzle member 24 supplies at
least part of the fibers F so that the fibers F extend over a layer
interface Pf between the resin layer Ps1 and the resin layer Ps2
formed in the molding tank 12 (the layer interface Pf of the
solidified portion Mh solidified by the laser beam Lc).
Accordingly, as compared with a configuration in which the nozzle
member 24 does not supply the fibers F so that the fibers F extend
over the layer interface Pf between the resin layer Ps1 and the
resin layer Ps2 formed in the molding tank 12, the molding strength
and molding accuracy of the three-dimensional molded part M are
increased.
Second Exemplary Embodiment
[0033] Next, an additive manufacturing apparatus 10 according to a
second exemplary embodiment is described. It is to be noted that
the same reference sign is applied to the portion equivalent to
that of the above-described first exemplary embodiment, and its
detailed description is omitted.
[0034] As shown in FIG. 4, in the additive manufacturing apparatus
10 according to the second exemplary embodiment, the resin powder P
is discharged by a coater 32 serving as an example of a discharging
unit. A blade 33 is provided around a discharge port 32A of the
coater 32. The blade 33 restricts scattering of the resin powder P
discharged from the discharge port 32A.
[0035] The coater 32 is movable in the radial direction (the
left-right direction in the drawing) at the upper side of the
molding tank 12, by a known moving mechanism (not shown). That is,
the coater 32 discharges the resin powder P from above into the
molding tank 12 by a constant amount while moving in the radial
direction from one end portion to the other end portion of the
molding tank 12.
[0036] The coater 32 temporarily stops discharging the resin powder
P and moving in the radial direction at the other end portion of
the molding tank 12, then moves to return to the one end portion of
the molding tank 12, and discharges the resin powder P into the
molding tank 12 while moving in the radial direction from the one
end portion to the other end portion of the molding tank 12
again.
[0037] Also, a reflector 31 is arranged above the molding tank 12.
The reflector 31 may change its angle by a mechanism (not shown). A
laser device 30 is arranged at a proper position in addition to the
laser device 20. The laser device 30 serves as a heating unit that
emits a laser beam Lf that provides scanning while reflected by the
reflector 31.
[0038] That is, in this second exemplary embodiment, the fibers F
are heated by the laser beam Lf emitted from the laser device 30.
Hence, in this second exemplary embodiment, the nozzle member 24 is
not provided with the heater 28. An example of the laser beam Lf
emitted from the laser device 30 may be a laser beam of a fiber
laser with a wavelength (for example, about 1 .mu.m) that is likely
absorbed by the fibers F.
[0039] An operation with the additive manufacturing apparatus 10
according to the second exemplary embodiment configured as
described above is described below. It is to be noted that
description on the operation common to that of the above-described
first exemplary embodiment is properly omitted.
[0040] The molding table 16 is arranged at the upper portion side
of the molding tank 12 by the up/down moving device 18. In this
state, the coater 32 discharges the resin powder P while moving in
the radial direction from the one end portion to the other end
portion at the upper side of the molding tank 12, and hence a layer
of the resin powder P, that is, a lowermost resin layer Ps0 (see
FIG. 5A) is formed on the molding table 16 in the molding tank
12.
[0041] Then, after the resin layer Ps0 is formed on the molding
table 16, the coater 32 moves to return to the one end portion of
the molding tank 12, and the nozzle member 24 supplies plural
fibers F to the resin layer Ps0. Then, the fibers F are heated and
molted by the laser beam Lf, which is emitted from the laser device
30 and provides scanning while reflected by the reflector 31, and
the fibers F are fixed to the resin layer Ps0.
[0042] As described above, also in the additive manufacturing
apparatus 10 according to the second exemplary embodiment, the
configuration is divided into the coater 32 that discharges the
resin powder P and the nozzle member 24 that supplies the fibers F.
Hence, as compared with a configuration not divided into the coater
32 that discharges the resin powder P and the nozzle member 24 that
supplies the fibers F, the orientation and mixture ratio of the
fibers F in the three-dimensional molded part M are properly
set.
[0043] Then, as shown in FIG. 5A, the coater 32 discharges the
resin powder P while moving in the radial direction from the one
end portion to the other end portion at the upper side of the
molding tank 12 again. Accordingly, a resin layer Ps1 is formed on
the resin layer Ps0. Then, after the resin layer Ps1 is formed, the
coater 32 moves to return to the one end portion of the molding
tank 12, and the nozzle member 24 supplies plural fibers F to the
resin layer Ps1 as shown in FIG. 5B.
[0044] Then, the fibers F are heated and molted by the laser beam
Lf, which is emitted from the laser device 30 and provides scanning
while reflected by the reflector 31, and the fibers F are fixed to
the resin layer Ps1. As shown in FIG. 5C, the area supplied with
the fibers F in the resin layer Ps1 is molten or sintered and
solidified (a solidified portion Mh is formed) by the laser beam
Lc, which is emitted from the laser device 20 and provides scanning
while reflected by the reflector 21.
[0045] The fibers F are heated and molten by the laser beam Lf
emitted from the laser device 30. Then, the fibers F are cooled,
solidified, and hence fixed to the resin layer Ps1. Accordingly, as
compared with a configuration not including the laser device 30
that emits the laser beam Lf, the orientation of the fibers F in
the three-dimensional molded part M is properly ensured.
[0046] Also, the nozzle member 24 supplies the fibers F after the
resin powder P is discharged, also for the lowermost resin layer
Ps0. Hence, as compared with a configuration in which the nozzle
member 24 supplies the fibers F before the resin powder P is
discharged (excluding a situation before the lowermost resin layer
Ps0 is formed), the coupling force between the fibers F and the
resin powder P is increased.
[0047] Then, as shown in FIG. 6A, the coater 32 discharges the
resin powder P while moving in the radial direction from the one
end portion to the other end portion at the upper side of the
molding tank 12 again. Accordingly, a resin layer Ps2 is formed on
the resin layer Ps1. Then, after the resin layer Ps2 is formed, the
coater 32 moves to return to the one end portion of the molding
tank 12, and the nozzle member 24 supplies plural fibers F to the
resin layer Ps2 as shown in FIG. 6B.
[0048] Then, the fibers F are heated and molted by the laser beam
Lf, which is emitted from the laser device 30 and provides scanning
while reflected by the reflector 31, and the fibers F are fixed to
the resin layer Ps2. Then, as shown in FIG. 6C, the area supplied
with the fibers F in the resin layer Ps2 is molten or sintered and
solidified (the solidified portion Mh is increased) by the laser
beam Lc, which is emitted from the laser device 20 and provides
scanning while reflected by the reflector 21.
[0049] By successively repeating the above-described steps, the
three-dimensional molded part M as shown in FIG. 4 is formed in the
molding tank 12. Although the illustration is omitted, as the resin
powder P discharged from the coater 32 is laminated on the molding
table 16, the molding table 16 is gradually moved downward by the
up/down moving device 18.
[0050] Also, as shown in FIG. 6C, the nozzle member 24 supplies all
the fibers F so that the fibers F extend over a layer interface Pf
between the resin layer Ps1 and the resin layer Ps2 formed in the
molding tank 12 (the layer interface Pf of the solidified portion
Mh solidified by the laser beam Lc). Accordingly, as compared with
a configuration in which the nozzle member 24 does not supply the
fibers F so that the fibers F extend over the layer interface Pf
between the resin layer Ps1 and the resin layer Ps2 formed in the
molding tank 12, the molding strength and molding accuracy of the
three-dimensional molded part M are increased.
[0051] The additive manufacturing apparatus 10 according to each of
the exemplary embodiments is described above with reference to the
drawings; however, the additive manufacturing apparatus 10
according to any one of the exemplary embodiments is not limited to
the illustrated configuration, and may be properly changed in
design within the scope of the invention. For example, the coater
32 may be used instead of the screen member 22 in the first
exemplary embodiment, and the screen member 22 may be used instead
of the coater 32 in the second exemplary embodiment.
[0052] Also, the nozzle member 24 does not have to be rotatable
around the direction intersecting with the up-down direction as the
axial direction. For example, plural nozzle members 24 with
different supply directions may be arranged and the nozzle members
24 may be properly selectively used, to change the angle (the
supply direction) of the fibers F to be supplied to the area where
the three-dimensional molded part M is formed.
[0053] Further, the nozzle member 24 does not have to eject and
supply the plural fibers F at once, and may eject and supply the
fibers F one by one. Also, the shape of the molding tank 12 does
not have to be a cylindrical shape, and may be, for example, a
rectangular tubular shape. Also, the solidifying unit is not
limited to the laser device 20 that emits a laser beam of a carbon
dioxide laser.
[0054] Further, in the second exemplary embodiment, the coater 32
does not have to temporarily stop at the other end portion of the
molding tank 12 and move to return to the one end portion of the
molding tank 12. For example, the coater 32 may discharge the resin
powder P while reciprocating between the one end portion and the
other end portion of the molding tank 12. Also, the heating unit is
not limited to the laser device 30 that emits a laser beam of a
fiber laser.
[0055] The foregoing description of the exemplary embodiments of
the present invention has been provided for the purposes of
illustration and description. It is not intended to be exhaustive
or to limit the invention to the precise forms disclosed.
Obviously, many modifications and variations will be apparent to
practitioners skilled in the art. The embodiments were chosen and
described in order to best explain the principles of the invention
and its practical applications, thereby enabling others skilled in
the art to understand the invention for various embodiments and
with the various modifications as are suited to the particular use
contemplated. It is intended that the scope of the invention be
defined by the following claims and their equivalents.
* * * * *